A ballistic pendulum involves hanging a hollow ball or object off of a string, which is the pendulum, vertically below the point at which the string hangs from. An object is then shot towards the ball. It is important to measure the final velocity of the pendulum to determine the initial velocity of the projectile.
When the two objects collide, kinetic energy is lost in the process of deformation. Therefore, the collision is an inelastic collision. After the ball embeds into the pendulum, their masses combine, so the velocity of the ball decreases because of the law of conservation of momentum.
Where m1 is the mass of the ball and m2 is the mass of the pendulum, the following must be true. . .
m1*v1 + m2*v2 = m1*v1initial + m2*v2initial
The initial velocity of mass 2 would be zero because the pendulum begins at rest. Therefore, the initial momentum would be the product of mass 1 and the initial velocity of mass 1. However, after the collision, the two masses would join together and have the same velocity. Therefore,
(m1 + m2)* v1 = m1 *v1initial
Therefore, the velocity of the projected ball would decrease after the collision since the mass is larger.
Ballistic pendulums are used to find the initial velocity of a projectile.
Lab 11 Ballistic Pendulum
A ballistic pendulum involves hanging a hollow ball or object off of a string, which is the pendulum, vertically below the point at which the string hangs from. An object is then shot towards the ball. It is important to measure the final velocity of the pendulum to determine the initial velocity of the projectile.
When the two objects collide, kinetic energy is lost in the process of deformation. Therefore, the collision is an inelastic collision. After the ball embeds into the pendulum, their masses combine, so the velocity of the ball decreases because of the law of conservation of momentum.
Where m1 is the mass of the ball and m2 is the mass of the pendulum, the following must be true. . .
m1*v1 + m2*v2 = m1*v1initial + m2*v2initial
The initial velocity of mass 2 would be zero because the pendulum begins at rest. Therefore, the initial momentum would be the product of mass 1 and the initial velocity of mass 1. However, after the collision, the two masses would join together and have the same velocity. Therefore,
(m1 + m2)* v1 = m1 *v1initial
Ballistic pendulums are used to find the initial velocity of a projectile.
Sources: http://hyperphysics.phy-astr.gsu.edu/hbase/class/phscilab/balpen.html
http://teacher.pas.rochester.edu/phy_labs/Conservation_Laws/Conservation_Laws.html